Bacterial DNA and immunostimulatory CpG oligonucleotides (CpG-ODN) activate the innate immune system to produce proinflammatory cytokines. Shown to be potent Th1-like adjuvants, stimulatory CpG-motifs are currently utilized as effective therapeutic vaccines for various animal models of infectious diseases, tumors, allergies, and autoimmune diseases. We have shown that it is possible to induce antigen specific Th2 immunity to myelin, using a co-vaccination strategy with DNA encoding IL-4 and myelin proteins. This approach ameliorated and actually reversed ongoing EAE. We recently discovered that the application of an immunoinhibitory GpG-ODN, with a single base switch from CpG to GpG, can effectively inhibit the immunostimulatory response of its CpG-ODN counterpart. Moreover, this inhibitory GpG-ODN is not only capable of counteracting the stimulatory effect of CpG-ODN in vitro, it is also capable of suppressing the disease severity of experimental autoimmune encephalomyelitis (EAE) in mice, a Th1-mediated animal disease model for multiple sclerosis, and inducing a Th2 shift, much as DNA co-vaccination with genes encoding myelin and IL-4 [Garren et al, 2001]. We will explore the utility of the GpG motif for therapy of autoimmune disease, and examine the underlying mechanism whereby it exerts its effects. We will extend pre-clinical studies on the mechanism whereby GpG-ODN induces reduced expression of MHC class II, promotes a Th2 shift, and enhances antigen specific Th2 responses. We will test a co-vaccination strategy using GpG-ODN plus genes encoding myelin to prevent and reverse acute EAE, and to block further relapses, if given after the initial acute attack in chronic relapsing EAE. We will use our recently developed proteomic myelin array to monitor epitope spreading and the nature of the T cell response, when DNA vaccines encoding myelin proteins are used to treat relapsing remitting EAE after the acute attack.